Secondary indexing with Redis. I haven’t seen this section of the official Redis documentation before, and it’s absolutely fantastic—well worth reading the whole thing. It talks through various ways in which you can set up indexes in Redis, mainly by leaning on sorted sets—which it turns out will binary lexicographically sort items with the same score. This makes it easy to implement autocomplete with Redis—but if you use them creatively you can implement subject/predicate/object graph searches or even N-dimensional range queries as well.